Yeah, nobody likes to give out drawings, even if they don't make it anymore. So, the original rim is not an LA378? Where did you come up with that number then? The pictures I can find of the DC70 it looks like the sprockets are originally made with a machined center plate and a welded on rim, yes? Can you measure the width of the rim, is it 55mm wide or 48mm wide? Not a lot of difference but it may be a clue. Place in Italy may have some rims that will work.
There has been a lot of suggestions that this model and some others were made for FIAT, badged as New Holland, by a company called Macmoter. They are no longer in existence and with the rearrangement of the FIAT/Case-New Holland-Kobelco-Hitachi, et al partnerships and joint ventures, there are lots of orphan stepchildren out there. My local New Holland parts guru told me he showed a price from NH of over $1,400 each for those sprockets, but no availability and he got the message "Contract Violation" so he couldn't order them even if somebody was crazy enough to pay that?
If I can find the right rim I may bring in a half dozen just to have for people that need them, not sure how many of these machines are out there but it's crazy for something this new to not have wear parts readily available. There was another guy on here looking for a DC70 final drive, I think I have that figured out but he just kind of disappeared before we confirmed it.